package LeetCode;

public class _141_环形链表 {
    public boolean hasCycle(ListNode head) {
    	if (head == null || head.next == null) {
			return false;
		}
        ListNode slow = head;
        ListNode fast = head.next;
        while (fast != null && fast.next != null) {
			slow = slow.next;
			fast = fast.next.next;
			if (slow == fast) {
				return true;
			}
		}
        return false;
    }
}
